For the first time, sludge waste from smolt production will be used to make biogas. The energy is used to heat the water for the fish. The residue can be mixed into inorganic fertiliser.
The first full-scale biogas plant from fish sludge is in operation. Sludge from Cermaq’s hatchery in Forsan, Northern Norway, is being used to efficiently produce biogas from the sludge from the waste water’s purification.
Has taken time to build up the bioculture
It’s estimated that around 500,000 kWh per year will be extracted from the waste from of nine million smolt. Cermaq uses the gas together with other energy to heat the water so that fish grow better.
“It has taken time to build up the bioculture but now gas is fully produced,” said Robert Eliassen, who is responsible for Sterner’s sludge operations at Sterner, a leading water treatment company in Norway.
The facility was opened in April 2018.
There is a requirement for cleaning of the wastewater before discharge which made Cermaq Norway want to look more closely at the possibility of gas production. Wastewater from aquaculture is rich in energy, which is now extracted in the form of combustible gas. The biogas production follows sludge production, which in turn results from varying feed consumption during the growth phase of the fish.
First use for fish sludge as a raw material
Cermaq’s sewage treatment plant collects around 260 tonnes of sludge annually, measured in pure dry matter. The sludge is a mixture of faeces and feeds spills from 1,600 tonnes of feed annually. The sludge previously represented a challenge both for storage and disposal. Fish from sludge differs from other types of sludge at a high nitrogen content, which requires a separate bioculture.
“There are many biogas plants in Norway. The unique thing about this plant is that it uses only fish sludge as raw material,” said Arne Hjalmar Knap, who has been responsible for the development of the technology at Sterner.
The new plant is the result of an R&D project and pilot plant at smolt producers Smøla Klekkeri and Settefiskanlegg. The bioculture was developped by by IMET (Institute of Marine and Environmental Engineering) at the University of Maryland. Enova has supported the development of the technology and the plant at Forsan.
10,000 tonnes of feed or more
Biotechnology is based on a system for biogas production called Anaerobic Baffle Reactor (ABR), and the technology has been further developed by Sterner for land-based farming.
“The economic advantage of this type of sludge treatment will depend on the size of the farm, and plants can be built for 5,000, 10,000 tonnes or larger amounts of feed per year,” said Robert Eliassen.
Economically and environmentally, the benefits are that sludge energy can be converted to methane, which can be used for the production of heat or a combination of electricity and heat. Recycling is therefore of great importance in the company’s climate change goals. Another advantage is that the dry matter (TS) is reduced by up to 70 per cent, so transported after is considerably reduced.
